One of the toughest aspects of 3D printing is to get your prints to stick to the build surface or bed platform. The following are the top five reasons you're having trouble and how to correct each issue:
1) Unlevel bed/printing surface -- The number one reason why you would have trouble with your parts not sticking is a uneven build plate. This problem can also lead to parts warping and/or gaps in between layers. Please make sure you have a level printing bed.
2) First layer gap -- Even if you have a completely level bed, the first layer height or gap between the nozzle and the bed is crucial to success. To check your 3D printer's first layer height try to slide a piece of copy paper between the nozzle and bed. You should be able to slide the paper back and forth easily but still feel some friction.
3) Bed Temperature -- If you have a heated bed, increasing the bed temperature will help get your parts to stick. This will ensure a better stick to your bed and will prevent parts from popping off.
4) Drafty room -- You might not be able to see it, but air flow through or around your 3D printer can cause problems with your prints and that includes sticking issues. Try to control the air that moves through your printing room so that you have a stable environment for printing.
5) Kapton tape, Painters Tape, and Hairspray -- When all else fails and you just can't get your prints to stick, there are some additional build surface preparations that might help. Spraying hairspray on your build glass helps with both PLA and ABS and is a very easy method to try. However, not all hairsprays work the same. We've found that super hold hairsprays work pretty well (we suggest a low-odor brand). For ABS users, Kapton tape can help to get your parts sticking and we also offer LEXAN build plates that help ABS stick surprisingly well. For PLA users, try the painters tape that is included with your printer for easy after-printing clean-up.